The present invention relates to a desk-top type cutter, and more particularly to an operating mechanism for rotating a safety cover which covers a circular saw blade.
In general, a desk-top type cutter for cutting a wood piece or lumber using a circular saw is well known. In such a desk-top type cutter, the circular saw is covered by a safety cover. Japanese Utility Model Examined Publication No. 62-5289 shows such a desk-top type cutter provided with a safety cover.
FIG. 5 is a side elevational view showing a desk-top type cutter disclosed in that publication. In FIG. 5, a reference numeral 101 denotes a table on which a support member 102 is mounted. A main body 103 of the cutter is pivotably mounted relative to the support member 102 through a support shaft 104 on the support member 102. Further, a safety cover 105 is rotatably mounted on the body 103, and a circular saw blade 106 is rotatably mounted so as to be covered by the safety cover 105. Also, a handle 107 is projected from a suitable portion of the body 103.
On the other hand, an operation lever 108 is pivotably mounted on the handle 107, and one end of a link piece 109 is held in abutment with a left (as viewed) end portion of the operational lever 108 in FIG. 5. One end of a wire 110 is connected to the other end of the link piece 109, and the other end of the wire 110 is in turn connected to a stud 112 of the safety cover 105 after passing through a guide portion 111 provided in the safety cover 105. A spring 114 is interposed between the stud 112 of the safety cover 105 and a stud 113 provided on the body 103, thereby normally biasing the safety cover 105 in a direction indicated by character a.
In such a desk-top type cutter, when it is desired to rotate the safety cover 105 against the biasing force of the spring 114 in the direction indicated by b in FIG. 5, first the operation lever 108 is rotated in the direction indicated by character c. Then, the link piece 109 is depressed in the direction d, so that the end portion, connected to the wire 110, of the link piece 109 is moved in the direction e against the biasing force of the spring 114. Thus, the safety cover 105 is opened by rotation in the direction of b. Under this condition, it is possible to cut the lumber or the like by the circular saw 106.
However, if the link mechanism is used in the safety cover for covering the circular saw, the number of the mechanical parts increases, making it difficult to assemble or fabricate the cutter. Also, since the wire is used in the force transmission mechanism, the force on the lever 108 is not effectively transmitted. Furthermore, since the spring member draws the safety cover and the force transmission mechanism, it is necessary to use a strong spring therefor, resulting in increased costs.
Furthermore, the prior art also discloses a portable hand tool provided with a latching mechanism for releasably latching or locking mechanism for releasably latching or locking a guard member for a rotary saw blade, such as disclosed in U.S. Pat. No. 4,693,008.
The portable circular power saw of this prior art reference has a releasable latching device including a pivotable latch member for releasably latching a guard member for a rotary saw blade in a guarding position. The latch member includes a hook engageable with a retaining notch of the guard member. The latch member is retained in a latching position by a spring-biased push rod and is moved to an unlatching position by operating the push rod. A permanent magnet mounted to the latch member cooperates with a ferromagnetic strip of the guard member to temporarily retain the latch member in its unlatched position as the guard member is rotated to an unguarding position. Thereafter, the permanent magnet and the ferromagnetic strip disengage from each other such that the latch member will automatically be returned to its latching position when the guard member is returned to its guarding position.
The hook of the latch member is engageable with a notch of the guard member for preventing rotation of, but not for transferring rotating force to, the guard member, i.e., the safety cover of the circular saw.
As described, the releasable latching device of this prior art reference comprises many members or parts such as a latch member, a push rod, a spring, a permanent magnet etc., which complicates the structure of the latching device, which is troublesome to assemble and involves high manufacturing cost.